Electrodynamic recording device



1952 H. c. ARENTZEN ELECTRODYNAMIC RECORDING DEVICE 2 SHEETSSHEET 1 Filed Jan. 10, 1948 Nov. 11, 1952 H. C. ARENTZE N EILECTRODYNAMIC RECORDING DEVICE 2 SHEETSSHEET 2 Filed Jan. 10, 1948 of the driven or feedback coil II in the substantially horizontal airgaps 8 at either side of the axis of rotation enables the whole oscillatory system to be built up of simpl and solid elements while simultaneously providing for convenient and efficient mounting of this system by means of the supporting member 16 comprising the resilient strip l8.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

1. In an electrodynamic recording device; a primary magnetic circuit defining two vertical air gaps, a secondary magnetic circuit defining two horizontal air gaps, an oscillatory system adapted to support a stylus and including a driving coil disposed in the vertical air gaps, a feedback coil disposed in the horizontal air gaps, and means for providing a substantially horizontal pivotal axis for said oscillatory system intermediate said vertical and horizontal air gaps.

2. In an electrodynamic recording device; a magnetic circuit defining two vertical and two horizontal air gaps, an oscillatory system including a stylus and a driving coil disposed to extend in said vertical air gaps, a feedback coil disposed in said horizontal air gaps, and means forming a substantially horizontal pivotal axis, said pivotal axis substantially coinciding with the center of gravity of said oscillatory system.

3. An electrodynamic recording device comprising a magnetic structure including two vertical and two horizontal air gaps, an oscillatory system including a stylus and holder therefor, a driving coil disposed on said holder and in said vertical air gaps and a feedback coil disposed on said holder and in said horizontal air gaps, a member supporting said oscillatory system in said magnetic structure and comprising a conical body provided with a, pair of grooves extending through said body and defining a resilient strip between two conical portions of said body, and fastening means at either end of said conical body to facilitate connection of said holder with said conical body and of said conical body with said magnetic structure, respectively.

4. In an electrodynamic recordingdevice; a magnetic structure, an oscillatory system including spaced apart vertical and horizontal air gaps, and supporting means for said oscillatory system and including a holder for a stylus, said supporting means comprising a conical body, said body being provided with two conical discs connected with each other by a relatively short resilient strip therebetween, and fastening means at either end of said conical body to facilitate connection of the latter to said magnetic structure and to said stylus holder, respectively, said resilient strip being disposed at a location between said vertical and horizontal air gaps.

, 5. In an electrodynamic recording device; a magnetic structure, an oscillatory system, and supporting means for said oscillatory system, said supporting means comprising a conical body, a

pair of grooves provided in said body and defining therebetween a relatively short resilient strip, and a threaded extension at either end of said body to facilitate fastening of said conical body to said structure and connection with a, stylus, respectively.

.6. An electrodynamic recording device comprisinga housing, a magnet within said housing, a first pair of pole pieces, an annular core of ferromagnetic material intermediate said first pair of pole pieces so arranged as to form two substantially vertical airgaps between said pole pieces and said core, a second pair of pole pieces and an annular body of ferromagnetic material so arranged as to form two substantially horizontal air gaps between said second pair of pole pieces and said annular body, an oscillatory system comprising a driving coil disposed in the vertical air gaps and a driven coil disposed in the horizontal air gaps, a holder member for said coils, a support extending into said member and affixed with one end therein and with the other end to a portion of said housing, said support comprising a resilient strip adapted to provide a substantially horizontal pivotal axis for said oscillatory system and being disposed at a level intermediate the levels at which said driving and driven coils are arranged, said strip forming a spring leaf which is substantially stiff and inflexible in all directions except against vibratory movements around said pivotal axis.

- 7. An electro-dynamic recording device comprising a ferromagnetic core member including a cylindrical portion having a longitudinal'axis, a pair of primary magnetic pole pieces of opposite polarity disposed at opposite sides of said core member and defining two substantially vertical air gaps lengthwise of said core member between it and said primary pole pieces, a pair of secondary magnetic pole pieces axially spaced from said primary magnetic pole pieces and terminating in substantially flat pole faces positioned adjacent said longitudinal axis, a ferromagnetic bridging member having surface portions facing said flat pole faces of said secondary pole pieces so as to define two substantially horizontal air gaps between said surface portions of said bridging member and said flat pole faces, and an oscillatory system mounted for pivotal movement about an axis extending between said primary and secondary pole pieces and perpendicularly to said longitudinal axis, said oscillatory system being adapted to carry a stylus, a driving coil surrounding said cylindrical portion of said core member so as to extend through said substantially vertical air gaps on both sides of said core member, and a feedback coil located in said substantially horizontal air gaps between said secondary pole pieces and said bridging member.

8. An electromagnetic recording device having an axis; comprising magnetic circuit means defining two substantially vertical air gaps in symmetrical positions with respect to a vertical plane and disposed in series in the magnetic path, and further defining two substantially horizontal air gaps in similar symmetrical positions with respect to said axis, said horizontal air gaps being axially spaced from said vertical air gaps and being likewise disposed in series in the magnetic path, and an oscillatory system mounted for pivotal move ment about a horizontal axis in said plane of symmetry and intermediate of said vertical and horizontalv air gaps, said oscillatory system including a stylus, a driving coil arranged to extend within said substantially vertical air gaps, and a feedback. coil arranged to extend within said substantially horizontal air gaps.

9. In an electrodynamic recording device; a magnetic structure including spaced apart vertical and horizontal air gaps, an oscillatory system includinga holder for a stylus, and supporting means for said oscillatory system comprising two conical disks connected with each other by a resilient strip therebetween, and fastening means at either end of said supporting means to facilitate connection of the latter to said magnetic structure an d to siaid stylus holder, respectively,

HOLGEQ CHRISTIAN ARENTZEN.

REFERENCES CITED The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Name Date Maxfield Apr. 28, 1925 Sawyer Apr. 28, 1931 Crouse Nov. 24, 1931 Guedon Mar. 19, 1935 Burt Apr. 25, 1939 Vieth June 6, 1939 Bobb Oct. 2, 1945 Faus Aug. 27, 1946 Albright Oct. 29, 1946 Wolff Feb. 8, 1949 

